1. Field of the Invention
The present invention relates to spinal column spacers and specifically to an anterior cervical column support device.
2. Description of the Prior Art
Several prior art spacers exist for repairing the spinal column. However, most spacers are designed for the lumbar or thoracic regions of the spine whereas most devices for repairing the cervical area of the spine usually involves some type of screw and rod system. The following U.S. Patents are examples.
U.S. Pat. No. 5,397,363 issued to Gelbard on Mar. 14, 1995 shows a spinal stabilization implant system. It uses plates and screws to stabilize the vertebrae of the cervical area. "The instant invention is a surgical implant system for the stabilization of the human spine by fixation of the vertebra. The system is based upon screws, nuts, rods, hooks, cross-members and variations thereof. The preferred embodiment employs a metal screw for placement in the sacrum or pedicle defined by a coarse self-tapping thread and a U-shaped saddle for placement of conventional alignment rods. Unique to this invention is that the screw is threaded on the outer surface of the saddle allowing the alignment rod to be securely fastened into the saddle by placement of the rod therein and the fastening of a nut to the top of the saddle. Further unique to this invention is the use of an elongated sagittal traverse support member that can accommodate the saddle protrusion either in a fixed position or by use of a rotatable insert that allows the cross member to be tightly fastened to the saddle in a variable alignment. The top-loading attachment is further applicable to caudal, cranial, and the like hook components. An anterior cervical plate is set forth using a second plate to permanently lock the cervical plate in position. The second plate does not rely upon the bone to support the place thus providing means to prevent any bone attachment screws from loosening or otherwise backing out of the bone."
U.S. Pat. No. 5,507,745 issued to Logroscrino et al. on Apr. 16, 1996 shows an occipito-cervical osteosynthesis instrumentation. It is another example of a rod-type system used on the cervical area of the spine. It comprises "two separate similar parts, namely a right and a left part, each formed by a cervical rod having asperities and an elongate occipital plate which forms one piece with said rod and extends said rod toward the occiput in the position of use, [an] adjustable means for anchoring the rod to the vertebrae and the plate to the occiput, each part being so preangulated and shaped as to be adapted to the anatomy of the occipito-cervical connection." This patent also recognizes that the cervical area of the spine requires a specific curvature for proper healing.
U.S. Pat. No. 5,713,900 issued to Benzel et al. on Feb. 3, 1998 shows an apparatus for retaining bone portions in a desired spatial relationship. The abstract states that it is "[a] apparatus for retaining first and second bone portions in a desired spatial relationship compris[ing] a first member positionable along the first and second bone portions. A second member connectable with the first bone portion has surface member defining an opening. A fastener is extendable through the opening in the second member to connect the second member to the first bone portion. The fastener has a first portion for engaging the first bone portion and a second portion for clamping the first member against the second member to fix the first and second members against relative movement. The first member is also connected to the second bone portion."
Very few references disclose the use of implantable spacers as a solution to cervical vertebra stabilization. Those that do, lack the advantages of the present invention.
The human spinal column consists of 33 (sometimes 34) vertebrae divided into five groups: cervical, thoracic, lumbar, sacral and coccygeal vertebrae areas. The sacral vertebrae are fused into a single bone as is the coccygeal vertebrae, usually designated as the coccyx. The movable vertebrae are found in the cervical, thoracic and lumbar areas. Each area has a characteristic curve. Various vertebrae differ in size and shape depending on the location in the spinal column. This means that a spacer designed for the lumbar or thoracic region will not perform properly in the cervical region. The present invention solves the problem of stabilization of the cervical vertebrae by providing a properly designed spacer for the cervical area.